Improving White Blood Cell Collection From Healthy Donors

Background: \- White blood cells called granulocytes help the body fight infection. People who have had chemotherapy or bone marrow transplants may have very low numbers of these cells. Transfusions of these cells can help improve the body's ability to fight infection. However, most of the cells are located in the bone marrow or spleen, and are hard to collect from healthy donors. Two drugs, filgrastim and dexamethasone, can help move the cells to the bloodstream to be collected by apheresis. Researchers want to study the best ways to collect these white blood cells. They also want to monitor the effects of the injections and donations on the volunteer donors. Objectives: \- To improve the amount and quality of granulocytes (white blood cells) collected by apheresis for donation. Eligibility: \- Healthy volunteers between 18 and 75 years of age. Design: * Participants will be screened with a physical exam and medical history. Initial blood tests will be done to check for eligibility. * Participants will donate granulocytes by apheresis a maximum of 12 times in 1 year. Donations will not usually be requested more often than every 4 weeks. Donors will be allowed to decline participation at any time. * Participants will have one injection of filgrastim 12 to 24 hours before donation. They will also have two tablets of dexamethasone 12 hours before donation. * White blood cells will be collected through apheresis. The apheresis will last about 2 hours. * Participants will be eligible to donate until they reach their 76th birthday.